Yes I have done research and read Wood-N-Things page.

I was reminded of my hard start when cold problem this morning. We got down to 60 here in OKC. It started but just took a little longer and had white smoke.

My engine oil temp reads 107. When I turn the key on I do not get anything from the side of the relay that goes to the glow plugs. I have 12v at every other post. When I give the pcm post a ground I can hear the relay click. Does this mean the relay is bad or what.

BTW I have had the hard start when cold for a while but have never seen the glow plug code until today. Will it throw a code because I messed with the relay, or because there actually is a problem.

I replaced the glow plugs in March when I did injectors. Motorcraft. I also have a new VC gasket and wire harness.

No I have not tried swapping the AIH relay yet.

 

Sounds like the relay may be good, but the PCM is not supplying the ground, basically the PCM is not telling the relay to kick on.

The code was likely from you grounding it out.

When you ground the relay, do you get 12V on the output of the relay? You might consider a momentary switch supplying a ground rather than PCM replacement.

 

I didnt test that....
If I do get 12v when I ground the relay then it means the PCM isnt sending the signal and is bad?

 

You should normally see a constant 12V at one of the large studs and both of the small studs. When the PCM energizes the GPR, it grounds one of the small studs which puts 12V across the coil and energizes the relay. If the GPR is clicking when you ground the PCM post, and there is no voltage on the large post going to the glow plugs, that means the relay is bad.

EDIT: If the ground isn't getting to the GPR, then it could be a PCM or wiring problem, as BigAl said. (looks like we were typing at the same time).

The AIH relay switches 12V to the air intake heater only and doesn't have anything to do with the glow plugs.

Chris

 

I know this but I was sure someone would ask if I tried swapping them to see if it would work. I have deleted the AIH so now it is a spare.

I will try grounding the relay and see if I get 12v at the GP post.

Thank you. Hopefully a bad relay.

 

It means either the PCM is bad, or another input, obviously not EOT because that is below the requirement to activate, is not good.

Seems like I only remember EOT and BARO(Internal to the PCM) coming into play though, but I will look through some information I have to see what inputs determine glow plug operation, others like AIT may come into play as well.

 

Yeah I read EOT and Baro

 

If I am not mistaken...The GPR will not send power to the glow plugs unless the engine oil temperature is less than 52 degrees farenheight. Just something to think about.
Dwayne

 

That is 55 degrees Celcius, or around 131 Fahrenheit.

 

Thanks for clarifying.

 

Did u see this writeup from years ago? It may help u with any lingering questions. My truck is one that quit supplying pcm ground. I have a momentary button that I mounted in the lip of the dash next to the steering column. When it is cold outside, i turn the key, count to 10 unless its really cold, and off we go.

Here is link.

https://www.ford-trucks.com/forums/7...pr-system.html

 

On a cold engine EOT should be a couple degrees different than ambient temp.

 

Thanks I will check it out

 

So I went out this morning when I knew the engine would be cold. Temp is 58 here. I tried to start and no dice. I wen and tested the relay and had .7v at the PCM input and nothing at the glow plug output. Then I heard it click and I had 12v at the PCM input. Then I jumped the relay and what do you know sh started. Looks like its jus the relay. Thank God! I wil swap in the AIH relay and get a stancor for standby.

 

Agreed. My Oil in the morning of 60 degree night is around 64. If your oil temp is 107 I would start their. I found the published for numbers for when things should happen are not always the most accurate.( At least for my truck) If nothing else you at least will have your oil temp sensor working for the other things.